Hydrogenation Of Nitrobenzene Research Articles

Theoretical evidence on pyridinic nitrogen in N, S-coordinated Co single atom catalyst as dominant active site promoting H2 cleavage, H diffusion, and hydrogenation activity

The limitation of isolated metal active sites in single atom catalysts (SAC) hinder their application in hydrogenation reactions, necessitating the creation of additional active site beyond the metal site. This study introduces pyridinic N and S atoms into the N/C sheet, optimally adjusting the local environment of the Co site. This adjustment synergistically enhances H2 activation, H diffusion, and promotes the hydrogenation of nitrobenzene into aniline. The sterically hindered Co acidic site and N basic site, known as frustrated Lewis pairs, in defect-containing Co-N3SN-def1 model cooperatively facilitate the highly efficient cleavage of the H2 molecule with a barrier of only 0.37 eV. The findings suggest that the pyridinic N site in the Co-N3SN-def1 model acts as a reservoir for *H, significantly contributing to the enhanced activity for the hydrogenation of nitrobenzene. The mechanism unveiled in this study offers valuable insights for designing efficient heterogeneous catalysts for target hydrogenation reactions.

Sophisticated construction of single-atom cobalt catalyst based on microbial hyphae for high-performance hydrogenation

Utilizing biomass as a versatile catalyst building platform holds tremendous promise for catalyst design. In this study, we demonstrate a facile and effective method to fabricate high-performance catalysts using Trichoderma afroharzianum hyphae derived carbon fiber (TAHCF) embedded with Co1-N3P1 active sites for nitroaromatic hydrogenation. This strategy leverages the intrinsic self-assembly and metal ion adsorption capabilities of Trichoderma afroharzianum (TA). During the carbonization process, amino acid-rich fungi undergo transformation into biochar substrates co-doped with functional heteroatoms, facilitating the creation of TAHCF single-atom catalyst. Moreover, the catalytic performance can be further enhanced by tailoring the coordination structure of metal atoms on the carbon substrates. Remarkably, we achieve a high turnover frequency of 1553 h−1 for the hydrogenation of nitrobenzene, along with exceptional conversion and selectivity for various nitro compounds with the metal loading as low as 0.02 wt%. Our study presents a characteristic synthetic method that advances the design of single-atom catalysts by leveraging the inherent structure characteristics of biomass in the pursuit of energy sustainability.

Site-Selective Bimetallic Heterogeneous Nanostructures for Plasmon-Enhanced Photocatalysis of Nitrobenzene Hydrogenation

Site-Selective Bimetallic Heterogeneous Nanostructures for Plasmon-Enhanced Photocatalysis of Nitrobenzene Hydrogenation

Solvent-free selective hydrogenation of nitroaromatics to azoxy compounds over Co single atoms decorated on Nb2O5 nanomeshes

The solvent-free selective hydrogenation of nitroaromatics to azoxy compounds is highly important, yet challenging. Herein, we report an efficient strategy to construct individually dispersed Co atoms decorated on niobium pentaoxide nanomeshes with unique geometric and electronic properties. The use of this supported Co single atom catalysts in the selective hydrogenation of nitrobenzene to azoxybenzene results in high catalytic activity and selectivity, with 99% selectivity and 99% conversion within 0.5 h. Remarkably, it delivers an exceptionally high turnover frequency of 40377 h–1, which is amongst similar state-of-the-art catalysts. In addition, it demonstrates remarkable recyclability, reaction scalability, and wide substrate scope. Density functional theory calculations reveal that the catalytic activity and selectivity are significantly promoted by the unique electronic properties and strong electronic metal-support interaction in Co1/Nb2O5. The absence of precious metals, toxic solvents, and reagents makes this catalyst more appealing for synthesizing azoxy compounds from nitroaromatics. Our findings suggest the great potential of this strategy to access single atom catalysts with boosted activity and selectivity, thus offering blueprints for the design of nanomaterials for organocatalysis.

Macrostructural Design Approach of the Monolithic Catalyst and Its Application in Nitrobenzene Hydrogenation

Macrostructural Design Approach of the Monolithic Catalyst and Its Application in Nitrobenzene Hydrogenation

MOO3 catalysed hydrogenation of nitrobenzene to aniline at near room temperature

MoO3 with orthorhombic structure (α-MoO3) was evaluated for its catalytic performance in the hydrazine-assisted transfer hydrogenation of nitrobenzene to aniline at near room temperature. The conversion of nitrobenzene, ca. 88.6 % was obtained after 4 h reaction with > 99 % of selectivity to aniline. The activation energy from the Arrhenius plot was ca. 120.6 kJ/mol. In this system, hydrazine (N2H4) did not only act as a hydrogen donor but also as a reducing agent to generate an active catalytic phase as supported by the existence of an induction period at the early stages of the reaction. XRD and XPS characterisations of the hydrazine–treated catalyst revealed the phase transformation from α-MoO3 to (NH4)0.23H0.08MoO3 containing Mo5+ species, a possible adsorption site for hydrazine decomposition to produce active hydrogen species for the transfer hydrogenation of nitrobenzene. Based on the Hammett plot, an anionic intermediate was indicated to be involved in the rate-determining step.

Heteroatom doping-induced Pt dispersion and electronic effect for boosting the catalytic performance in the hydrogenation of nitrobenzene to p-aminophenol

N-doped carbon materials were synthesized using a straightforward salt template method for Pt metal modification, resulting in a reduction in particle size from 4.8 nm to 2.1 nm due to the interaction between Pt and the carrier. The hydrogenation activity of nitrobenzene increased by 4.5 times compared to undoped catalysts. Additionally, the electronic effects of N and Pt enhanced the selectivity of p-aminophenol by up to 20.4 %. The anchoring of Pt by N improved the stability of active metal centers in a strong acidic system, thereby retarding Pt loss. Theoretical calculations and characterization revealed that the enhancement of activity relied on the high dispersion of Pt, while the improvement in product selectivity was associated with changes in the adsorption strength of the phenylhydroxylamine intermediate. N anchoring of Pt, inducing an electron effect, disentangled the activity and selectivity of nitrobenzene hydrogenation for the preparation of p-aminophenol.

Iron-Based Catalysts with Oxygen Vacancies Obtained by Facile Pyrolysis for Selective Hydrogenation of Nitrobenzene.

The development of preparation strategies for iron-based catalysts with prominent catalytic activity, stability, and cost effectiveness is greatly significant for the field of catalytic hydrogenation but still remains challenging. Herein, a method for the preparation of iron-based catalysts by the simple pyrolysis of organometallic coordination polymers is described. The catalyst Fe@C-2 with sufficient oxygen vacancies obtained in specific coordination environment exhibited superior nitro hydrogenation performance, acid resistance, and reaction stability. Through solvent effect experiments, toxicity experiments, TPSR, and DFT calculations, it was determined that the superior activity of the catalyst was derived from the contribution of sufficient oxygen vacancies to hydrogen activation and the good adsorption ability of FeO on substrate molecules.

Size control of Pt nanoparticle catalysts for high-selectivity hydrogenation of nitrobenzene to p-aminophenol

Liquid-phase hydrogenation reaction of nitrobenzene to p-aminophenol (PAP) is investigated using a series of Pt-based catalysts, where activated carbon served as support and ethylene glycol (EG) as the reducing agent and solvent. Different platinum sources are employed to obtain Pt/C catalysts with different Pt metal particle sizes, as determined by transmission electron microscopy. The underlying mechanism of nitrobenzene selective hydrogenation on different size of Pt clusters have been systematically investigated. Characterization and catalytic tests show that the catalytic performance of the Pt-based catalyst is deeply influenced by particle size, where the size around 2.5 nm exhibits a suitable hydrogen absorption and activation ability, leading to the best catalytic performance. Under the optimal reaction conditions, the PAP selectivity reached 76.4 % and the conversion of NB reached 100 %. Moreover, the catalyst displayed strong recyclability with the PAP selectivity remaining above 70 % after five cycles of the catalyst, which would enable promising industrial applications.

Selective electrochemical hydrogenation of nitrobenzene to aniline coupled with efficient 5-hydroxymethylfurfural oxidation in aqueous electrolyte using a broccoli-like CuNi catalyst

Selective electrochemical hydrogenation of nitrobenzene (NB) to aniline (AN) remains a huge challenge, and it is highly imperative to develop efficient and nonprecious electrocatalysts with superior stability. Herein, an earth-abundant Cu60Ni40 electrocatalyst is prepared by a simple galvanostatic deposition approach, which endows splendid electrocatalytic activity and robust stability in the nitrobenzene electroreduction with AN selectivity of ∼100 %. In-situ attuned total reflection Fourier transform infrared spectroscopy (ATR-FTIR) monitors the intermediates to disclose the reaction pathway. It mainly follows the direct route to AN instead of condensation route to azoxybenzene (AOB). Density functional theory (DFT) calculations confirm that the adsorption configuration and capability towards NB are effectively regulated owing to the synergy of bimetal catalysts and the optimized adsorption of H* facilitates the proton-coupled electrochemical reduction process, yielding AN with high selectivity. In addition, the two-electrode electrolyzer (CuNi NTs||CuNi) is successfully assembled to reduce NB to AN at the cathode and concurrently oxidize biomass platform molecule 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic (FDCA) at the anode with both yield of ∼100 %, demonstrating improved energy utilization efficiency. These findings might prove the way for rational design of non-precious and highly durable electrocatalysts for co-electrolysis systems to produce high-value added chemicals without carbon emission.

Insights into the Mechanism of Nitrobenzene Reduction to Aniline by Phosphomolybdic Acid Supported TM1 Single-Atom Catalysts.

Catalytic hydrogenation of nitrobenzene (Ph-NO2) to aniline (Ph-NH2) is a model reaction in the field of catalysis, in which the development of efficient catalysts remains a great challenge due to the lack of strategies to solve activity and selectivity problems. In this work, the mechanism of Ph-NO2 hydrogenation over Pt1 supported on phosphomolybdic acid (α-PMA) was proposed by density functional theory (DFT) calculations. The results show that the dissociation of the first and second N-O bonds is triggered by single H-induced and double H-induced mechanisms, respectively. The limiting potential of the reaction process is -0.19 V, which is the smallest potential in the field of Ph-NO2 reduction reaction to date. In the whole reaction process, the catalytic active site is the Pt atom, and polyoxometalate plays the role of an electronic sponge in the reaction. Additionally, based on experimentally confirmed Pt1/Na3PMA, the reduction capacity of Pd1/Na3PMA toward Ph-NO2 was predicted by DFT calculation. The distinctive adsorption patterns of Ph-NO2 on Pt1/Na3PMA and Pd1/Na3PMA were elucidated using the DOS diagram and fragment molecular orbital analysis. We anticipate that our theoretical calculations can provide novel perspectives for experimental researchers.

MoOx regulating Ni-based catalyst anchored on N-doped carbon microspheres for catalytic hydrogenation of nitroarenes

Reasonable modification of Ni-based catalysts is crucial for improving their catalytic activity in the nitroarenes hydrogenation but remaining a major challenge. Herein, a MoOx-promoted Ni-based bimetallic catalyst with fine Ni nanoparticles (only about 5.7 nm) anchored on N-doped carbon microspheres (NiMo1@NC-500) was prepared for the first time by a simple one-pot hydrothermal strategy and exhibits excellent catalytic activity for the probe reaction of nitrobenzene hydrogenation. The characterization and DFT calculations results elucidated that Ni and MoO2 sites promoted the activation and adsorption of H2; while the NiNx sites significantly enhanced the adsorption of the reaction substrate nitrobenzene. This synergistic adsorption mode endowed the catalyst with excellent nitrobenzene hydrogenation performance under mild conditions (80 °C, 1 MPa H2, 3 h). Moreover, the as-prepared catalyst exhibited robust stability for no less than 6 cycles and outstanding generality for the hydrogenation of other substituted nitroarenes, which provide a profound insight for the preparation of efficient and economical catalysts for the reduction of nitroarenes.

Tuning the electronic structure of Pd by the surface configuration of Al2O3 for hydrogenation reactions.

The electronic interaction between a metal and a support modulates the electronic structures of supported metals and plays an important role in manipulating their catalytic performance. However, this interaction is mainly realized in heterogeneous catalysts composed of reducible oxides. Herein, we demonstrate the electronic interaction between γ-Al2O3 and η-Al2O3 with varying acid-base properties and supported Pd nanoparticles (NPs) of 2 nm in size. The strength and number of acid-base sites on the supports and catalysts were systemically characterized by FT-IR spectroscopy and TPD. The supported Pd NPs exhibit electron-rich surface properties by receiving electrons from the electron-donating basic sites on γ-Al2O3, which are beneficial for catalyzing the hydrogenation of nitrobenzene. In contrast, Pd NPs loaded on η-Al2O3 are electron-deficient because of the rich electron-withdrawing acid sites of η-Al2O3. As a result, Pd/η-Al2O3 exhibits higher catalytic activity in phenylacetylene hydrogenation than Pd/γ-Al2O3. Our results suggest a promising route for designing high-performance catalysts by adjusting the acid-base properties of Al2O3 supports to maneuver the electronic structures of metals.

Synthesis of p-aminophenol by transfer hydrogenation of nitrobenzene with formic acid as a hydrogen source

Synthesis of p-aminophenol by transfer hydrogenation of nitrobenzene with formic acid as hydrogen source.

Novel TPMS carbon-based monolithic catalysts by three-dimensional printing for enhancement of nitrobenzene hydrogenation reaction

Preparation of periodic curved surface, structured, carbon-based catalysts using a 3D printing method achieved good results in the hydrogenation of nitrobenzene to aniline in a packed-bed micro-reactor.

Nitrogen-doped carbon material NCM-T heterogeneously catalyzed liquid-phase hydrogenation of nitrobenzene to aniline

N-doped carbon materials NCM-T are prepared by in situ doping for the heterogeneous catalytic liquid-phase hydrogenation of nitrobenzene to aniline. Changes in the N species conformation and their relationship with catalytic activity are discussed.

Interfacial coupling of transition-metal composites with nitrogen doped carbon as efficient catalysts for nitro-compounds hydrogenation

A general strategy for developing nitrobenzene hydrogenation catalysts through constructing interfacial engineered in transition-metal compound with nitrogen doped carbon is proposed. The interfacial bonds in achieved catalysts can modulate the...

Copper-Catalyzed Continuous-Flow Transfer Hydrogenation of Nitroarenes to Anilines: A Scalable and Reliable Protocol.

A robust supported catalyst that is made up of copper nanoparticles on Celite has been successfully prepared for the selective transfer hydrogenation of aromatic nitrobenzenes to anilines under continuous flow. The method is efficient and environmentally benign thanks to the absence of hydrogen gas and precious metals. Long-term stability studies show that the catalytic system is able to achieve very high nitrobenzene conversion (>99%) when working for up to 145 h. The versatility of the transfer hydrogenation system has been tested using representative examples of nitroarenes, with moderate-to-excellent yields being obtained. The packed bed reactor (PBR) permits the use of a setup that can provide products via simple isolation by SPE without the need for further purification. The recovery and reuse of either EG or the ion-exchange resin leads to consistent waste reduction; therefore, E-factor distribution analysis has highlighted the environmental efficiency of this synthetic protocol.

Development of Magnetizable, Nickel-Ferrite-Decorated Carbon Nanocomposites as Hydrogenation Catalyst for Aniline Synthesis.

Catalysts with magnetic properties can be easily recovered from the reaction medium without loss by using a magnetic field, which highly improves their applicability. To design such systems, we have successfully combined the magnetic properties of nickel ferrite nanoparticles with the positive properties of carbon-based catalyst supports. Amine-functionalized NiFe2O4 nanoparticles were deposited on the surfaces of nitrogen-doped bamboo-like carbon nanotubes (N-BCNT) and carbon nanolayers (CNL) by using a coprecipitation process. The magnetizable catalyst supports were decorated by Pd nanoparticles, and their catalytic activity was tested through the hydrogenation of nitrobenzene (NB). By using the prepared catalysts, high nitrobenzene conversion (100% for 120 min at 333 K) and a high aniline yield (99%) were achieved. The Pd/NiFe2O4-CNL catalyst was remarkable in terms of stability during the reuse tests due to the strong interaction formed between the catalytically active metal and its support (the activity was retained during four cycles of 120 min at 333 K). Furthermore, despite the long-lasting mechanical stress, no significant palladium loss (only 0.08 wt%) was detected.

Surface oxygen vacancies of TiO2–x enabled water transfer photocatalytic hydrogenation of nitrobenzene to aniline without use of co-catalyst

Water transfer photocatalytic hydrogenation of nitrobenzene to aniline is an attractive and environmentally friendly process in chemical manufacturing. Herein, through an in-situ CO reduction pathway, the TiO2-based photocatalysts with surface and subsurface VOs are prepared for water transfer hydrogenation of nitrobenzene to aniline. The CO originated from incomplete combustion of residual organic compounds of the TiO2 precursor (tetrabutyl titanate), can react with the lattice oxygen of TiO2 and obtain rich surface and subsurface VOs TiO2-based photocatalysts without additional reduction reagent. The as-prepared TiO2 catalyst exhibits a desired band structure and rapid separation of photogenerated carriers. Besides, the TiO2 catalyst with surface and subsurface VOs can stabilize intermediates for water transfer hydrogenation. Thus, compared with heteroatom doping and poor-VOs TiO2, the TiO2 catalyst exhibits highly selectivity and conversion for photocatalytic hydrogenation of nitrobenzene substrates without the use of any cocatalyst and reductant H2.